Process of manufacture of aviation gasoline blending stocks



Julyv 9, 1946; w. A. scHuLzrz E rAL 2,403,379

' PROCESS o F MANUFAGTURE oF AVIATION GAsoLINE BLENDING sTocKs FiledMarch 10, 1944 v Patented July 9, 1946 PROCESS F MANUFACTURE 0F AVIATIONGASOLINE BLENDING STOCKS Walter A. Schulze and Carl J. Helmers,Bartlesville, Okla., assignors to Phillips Petroleum Company, acorporation of Delaware Application March 10, 1944, Serial No. 525,922

13 Claims. (Cl. 260-671) This invention relates to the production ofhigh octane hydrocarbon fuels by the catalytic conversion of petroleumhydrocarbons. More specifically the invention relates to the productionof aromatic hydrocarbon concentrates suitable for inclusion in aviationgasolines through a novel sequence of catalytic operations.

The production and recovery of aromatic hydrocarbons from petroleumsources are of particular importance in supplying large quantities ofbenzene, toluene, ethylbenzene, cumene and other compounds needed assolvents, gasoline blending agents and intermediates in organic chemicalindustries. Recently, the demand for high-quality aviation gasolines hasgreatly increased the demand for aromatic hydrocarbons because of theextra power in rich-mixture performance derived fromaromatics-containing gasoline blends. In order to augment the supply ofaromatic distillates, thermal and catalytic cracking of petroleumhydrocarbons have been employed to produce aviation blending stocks withthe latter processes producing products superior to the straight thermalprocedures. However, it is well known that heretofore in order toproduce high-quality aromatic distillates relatively severe conditionsof catalytic cracking were required, often involving multiple-passcatalytic cracking operations. Under such conditions the production oflight gases may amount to 50 weight per cent or more of the originalcharge stock. It is obvious then that the present catalytic crackingprocesses are not entirely satisfactory in view of the low yieldsrealized and the plant equipment required for multiple-pass catalyticoperations.

The employment of aromatic concentrates in aviation gasolines iscontingent not only upon a high aromatics concentration in the blendingstocks to impart desirable performance characteristics, but also on verylow proportions of undesirable hydrocarbon types which impair theblending 3-C octane values of the aromatics-rich fractions. The qualityof the aromatic blending stks as measured in flight tests and by the S-Csupercharged engine can often be greatly improved by the substantiallycomplete removal of non-hydrocarbon impurities such as sulfur compounds.It is also recognized that further quality improvement can be eifectedby conversion of the benzene content of blending stocks to higherhomologs through alkylation with olens such as ethylene, propylene andbutylenes.

It is an object of this invention to accomplish the conversion ofselected hydrocarbon feed stocks to gasoline of unusually high aromaticcontent and relatively free of undesirable hydrocarbon andnon-hydrocarbon impurities by means of an interrelated sequence ofcontrolled catalytic operations.

Another object of this invention is to increase the yield and quality ofblending stocks for aviation gasoline by means of combined catalyticalkylation and treating steps.

Still another object of this invention is the provision of an integratedprocess for the production of aromatic blending stocks of low sulfur andolen content through the catalytic treatment of selected fractions ofthe raw aromatic product.

Other objects and advantages of the invention will. be apparent from thefollowing disclosure.

We have discovered that the production of gasoline stocks rich inaromatic hydrocarbon types may now be accomplished without recourse tomultiple-pass catalytic cracking operations. Subsequent to therelatively mild operating conditions employed in the catalyticaromatization of the present process, -a substantial increase in therich mixture rating of the aviation base stock is effected by acombination of two outstanding novel features: (l) segregation of thebenzene fraction followed by alkylation with the olenic constituentsfrom the primary catalytic reaction to produce alkyl benzenes greatlysuperior to benzene in rich mixture blending Value; (2) application of acatalytic treating operation to the product stream to remove deleteriousimpurities thereby greatly improving the rich-mixture rating of the basestock.

The beneficial results realized from the above features are such thatthe utility of catalytic cracking oper-ations has been greatly extended.Of inestimable value is the conservation of feed stocks, since with ournovel process it is now possible to produce a high quality aromaticdistillate with less severe cracking conditions for a given S-C rating.The aromatics content of the finishedv blendingstock is increased byvirtue of the alkylation of the benzene fraction, since freezingv pointconsider-ations often preclude the inclusion of the total benzenefraction as such. Another important advantage of the present process isthat the range of operable feed stocks has been greatly extended in viewof the quality increase that can be realized from the combined elects ofthe alkylation and the treating operations.

Considering only its broader aspects, the present process may beoperated in the following manner to accomplish the objects andadvantages previously set forth. Ordinarily a petroleum distillatehaving a high carbon -to hydrogen ratio is catalytically cracked undercyclization conditions with subsequent stabilization of the eliluent.The light gas is processed to prepare an oleflnic alkylation feed whilethe stabilized gasoline is claytreated and separated by fractionationinto a 200 F. end-point benzene-containing stream and a higher-boiling350 F. end-point aviation blending stock. The lower boiling fraction istreated catalytically under polymerizing conditions to remove sulfur andoleiinic material, both of which are undesirable in the subsequentalkylation step. A purified and refractionated benzene-concentrate iscatalytically alkylated with any one or any combination of the lightolens previously produced in the primary conversion. The lean benzeneeffluent stream from the alkylation step is recycled to the crackingstep while the total alkylate is fed directly into the mainunfractionated product stream where its valuable constituents aresegregated in the 350 F. end-point stock. This latter material is thencatalytically treated under polymerizing conditions to produce afinished product of high rich-mixture blending value. The secondarypolymerization and alkylation steps of this process not only coact toexert a direct favorable effect on the volume and quality of finishedproduct, but they also contribute valuable recycle stock of high carbonto hydrogen ratio to the primary conversion step thereby furtherincreasing the yield of aromatics as based on fresh feed.

The accompanying simplified drawing shows one specific diagrammaticarrangement of apparatus by which the present process may be carriedout. It should be understood, however, that the invention is not limitedto processing as herein disclosed and that Various modifications of theprocess and apparatus may be made without departing from the scope ofthe invention as defined in the appended claims.

Referring to the drawing, a thermally or catalytically cracked naphthahaving a high carbon to hydrogen ratio is transmitted from a charge tanki into a line 2 that communicates with a recycle stock line 'Il and asteam supply line 3. The resulting mixture of naphtha, recycle stock andsteam constitutes a composite feed that is preferably in a vaporousstate and that is passed into a heating coil il. The feed is preheatedto about 1100-1150 F. in heater l prior to injection into a catalystcase 5 which is filled with a solid adsorbent-type catalyst such asbauxite and in which conditions of temperature, pressure and Contacttime are selected so as to result in optimum aromatics formation. Theefuent from the catalyst case is conducted through a line 6, a vheatexchanger l and a line 8 to a separator 9 where condensed steam isremoved by means of a line i0. Gaseous products are separated in this istep and are conducted via a line l l, a compressor l2 and a line I3 toa high-stage accumulator i4. In this latter unit further condensation ofwater along with small quantities of hydrocarbon is ef fected and thecondensate is drained through line I5. The gaseous products then passvia a line I6 'to a column i'! where they are contacted with absorbingliquid from a line 6I to remove C5 and heavier hydrocarbons. The richabsorbing liquid is then returned to the main product stream via linesi8 and 25. The C4 and lighter gases are conducted through a line i9 to afractionator 20 where hydrogen and methane are the .principal componentsof the overhead fraction that are removed through a line 2| while thekettle product is transferred in a line 22 to a column 23 where a gasfraction comprising C2, Cs, and C4 hydrocarbons is prepared and chargedto an alkylation unit 45 via a line 2e. The small quantity of Ct--hydrocarbons comprising the kettle product of column 23 is added to themain product stream through line 25.

The stabilized product stream from separator 9 is withdrawn through aline 21, preheated in heat exchanger 1 and finally discharged into a(lil flash vaporization tower 26. Normally liquid product hydrocarbonsfrom the gas plant and alkylation operations are conveniently added atthis point from line and preheater 2S. The overhead vapors ofapproximately 400 E. P. are conducted through a line to a clay-tower 3|While the high boiling components are discharged into a recycle line 68through a line 29. The clay-tower eiiiuent is discharged via a line 32into a fractionator 33 where the product stream is divided forsubsequent processing.

The overhead stream from 33 is comprised of hydrocarbons boiling from C5to 200 F. and is relatively rich in benzene and oleiins. This materialis passed through a line 34 to a heater 35 where its temperature israised to a suitable value of about 400 F. under sufcient pressure tomaintain substantially liquid-phase conditions, The hot liquid isdischarged directly into a catalyst case 3S which is filled with thepreferred silicaalumina catalyst composition. The treated efuent ispartially vaporized in line 31 as the pressure is reduced andfractionation is effected in a column 38. A fraction having an end-pointof about 160 F. is taken overhead to motor fuel storage through a line39 while the kettle product is taken Via a line 4i] to a fractionator Mwhere a benzene concentrate boiling between M-180 F. constitutes theoverhead product and the kettle product containing olen polymer isremoved through a line 43 to the recycle line 68.

The benzene concentrate from column #il is utilized as feed stock forthe alkylation step along with the olefins prepared in column 23. Thebenzene stream from line i2 is combined with the oleiin-parain gasesfrom line 26 just ahead of heating coil 45. The alkylation charge ispreheated to alkylation conditions under a pressure sufficient tomaintain liquid or dense phase conditions and is discharged directlyinto the alkylation reactor d5. The catalyst case may be filled with asilica-alumina catalyst composition. The reactor effluent is conductedthrough a line lll with pressure reduction into a column 48 where theproduct is stabilized with the light parafns and any unreacted olefmsbeing removed through a line to be employed as renery fuel or in otherconversion operations. The kettle product is suitably preheated and istransferred through a line 50 to a fractionator 5| where the unreactedbenzene along with the naphthenic and paraffinic constituents of theoriginal benzene concentrate are conducted through a line 53 to therecycle transfer line yESB: The kettle product from 'i column 5i whichcontains a mixture of monoand di-alkylated benzene derivatives is passedthrough lines 52 and 25 into heater 26 and thence into line 2l, the mainstabilized product stream from the catalytic cracking operation. In thismanner alkylate boiling below about 400 F. is passed on to furthertreatment and the highboiling alkylate finds its way into the recycleline ES via line 29.

After removal of the 200 F. end-point fraction in column 33, the mainaviation base stock material, which now includes aromatics reconstructedfrom the olens and benzene as well as aromatics produced in the originalcracking step, is passed through a line 513 into a fractionator 55. Afraction boiling between 20G-350 F. is taken overhead in a line 51 whilematerial distilling above 350 F. is discharged through line 5S intorecycle line 6o. A portion of the overhead cut is diverted into a line58, a condenser 59 and a reflux tank 50. The condensed material not onlyfurnishes reflux for column 55 but also constitutes absorbing liquidwhich is pumped through a line El to column Il.

The product in line 5'." is heated in a coil ft2 to a temperature ofabout 450 F. under pressure adequate to maintain liquid-phase conditionsduring the subsequent treatment in a catalyst case G3. After furtherreduction of sulfur and unsaturation over the preferred silica-aluminacatalyst, the product is transferred via a line 64 to a fractionator E5.High-boiling polymers and sulfur compounds are removed through a line 06and an overhead 20G-350 F. fraction is taken to storage as finished basestock through a line 6l.

The recycle stock in line 63, which comprises high-boiling hydrocarbonsfrom columns 28, lil, 55 and 85 as Well as a light overhead fractionfrom column 5 l, is passed through heat exchanger 7 into a tar trap 69Where partial vaporization occurs. High boiling refractory hydrocarbonsand sulfur compounds are removed through a line lil While the vapors areconducted through line 'H to fresh-feed line 2.

The preceding description has broadly outlined the mode of operation fthe present invention. However, since the total C4 and lighter olefinsare `produced. in a molar excess with respect to benzene, severalalternative operations should be considered with respect to the mosteconomical utilization of these by-product streams.

Thus, where it is desired to realize maximum conversion of light olefinsto aromatic derivatives, the employment of benzene from some externalsource is necessary. Make-upbenzene in sufficient quantity to equal orexceed the molar quantity of light olens may be withdrawn from storagethrough line id and mixed with the 1GO-18()0 F. fraction in line di?.Subsequent to alkylation in 4S and fractionation in column 48, theexcess benzene and inert parafns and naphthenes are taken overhead inline 53 from column 5l. In cases where benzene-olefin mol ratios of 2:1to 4:1' have been employed, it is undesirable t0 recycle this materialto the cracking reaction as previously described. Instead a majorportion lof this stream is diverted from line 53 into 53a and thenceinto line 52 from which it is returned to the main product stream. Inthis Way the excess benzene is recovered along With benzene derived fromthe cracking reaction Without adversely affecting the equilibrium in thecracking step. However, a minor portion of the overhead from column 5imust be recycled via lines 53, E58, heat exchanger tar trap 69 and line'Il in order to prevent pyramiding of the parafns and naphthenes in thebenzene concentrate. This mode of operation permits the inclusion ofappreciable quantities of high quality benzene homologs in the G-350Q F.product fraction.

In those instances where employment of excess b-enzene is not practical,it is usually desirable to convert the available benzene to the mostvaluabie benzene homolog, cumene. Fractionator 20 in the gas recoverysystem is operated so as to remove hydrogen, methane and ethylene.Column 23 is then employed to prepare a Ca fraction for the alkylationreactor While the C4 fraction is removed via line 25a for use as feed tocodimer operation or isobutane alkylation. In the benzene-propylenealkylation, maximum conversion of benzene is sought, hence the overheadfrom fractionator El may be recycled to the catalytic cracking step vialines 53 and 68 as originally described. The cumene and di-isopropylbenzene is transferred via lines 52, 25 and heater 26 to the mainproduct stream in line 21. The richmixture blending value of the final20D-350 F. fraction is greatly increased by the inclusion of this cumenederived exclusively from the by- 1products of the original catalyticcracking operaion.

Similar variations in the gas recovery system may be effected in orderto produce ethylbenzene or mixed ethylene and propylene derivatives ofbenzene.

The process of this invention can utilize a variety of feed stocksincluding: straight run and cracked gasoline, virgin and crackednaphthas and gas oil. However, Where cracking and aromatization arecombined in one operation. a's in the case of virgin naphtha feed,severe temperature conditions are required resulting in considerableformation of dry gas. The preferred feed is a thermally or catalyticallycracked gasoline of high carbon to hydrogen ratio and having an ASTMboiling range of about to 400 F.

The catalytic steps of the present process in the order of o-ccurrenceare: (1) aromatization, (2) polymerization and (3) alkylation.

The catalyst for the primary conversion to aromatics is preferably analumina base material which may be of natural or synthetic origin. Apreferred catalyst is the naturally occurring mineral bauxite althoughother catalysts of suitable activity and properties may be used such assynthetic alumina promoted with minor proportions of other metal oxides.

The process operations involving treatment of selected product streamsunder polymerizing and alkylating conditions are carried out oversilicaalumina type catalysts. In general these catalysts are prepared byfirst forming a hydrous silica gel from an alkali silicate and an acid,extracting soluble material With water, activating the gel with anaqueous solution of a suitable metal salt, and subsequently washing anddrying the treated material. In this manner, a part of the metalpresumably in the form of a hydrous oxide, is selectively adsorbed bythe hydrous silica and is not removed by subsequent washing.

More specifically, the preferred type of silicaalumina catalyst isprepared by treating a Wet or partially dried hydrous silica gel with analuminum salt solution, such as a solution of aluminum chloride orsulfate, and finally washing and drying the treated material. However,catalysts of a very similar nature but differing among themselves as toone or more specific properties may be prepared by using a hydrolyzablesalt of a metal selected from group IIIB or from group IVA of theperiodic system, and may be referred to in general as silica-aluminatype catalysts. More particularly, salts of indium and thallium inaddition to aluminum in group IIIB may be used, and salts of titanium,zirconium and thorium in group IVA may be u'sedto treat silica gel andto prepare catalysts of this general type. Whether prepared by thismethod or by some modification thereof, the catalysts will contain amajor portion of silica anda minor portion of metal oxide. This minorportion of metal oxide, such as alumina, will generally not be in excessof 10 per cent by Weight, and will more often be between about 0.1 and1.5 to 2 per cent by weight.

The primary catalytic conversion or aromatization stage 0f this proces-sis carried out over the preferred bauxitecatalyst at temperaturesranging from about 1050 to about 1250 F. Moder- ".7 atelysuperatmospheric pressures are recommended for this reaction such asthose extending from atmospheric to about 200 pounds per square inchgage. In many instances it may be desirable to employ a diluent such assteam to aid in temperature control.

One of the features of the present invention is the second stagecatalytic treatment of the product stream under polymerizing conditionsover the silica-alumina catalyst to elect an ultimate reduction of olenand sulfur content. This operation is preferably conducted as aliquid-phase operation. Pressure in the reactor may vary from about 500to 2000 pounds gage with a preferred range of about 800 to 1500 pounds.

Operating temperatures for the polymerizing treatment may extend fromatmospheric to about 700 F. depending on the characteristics of theoriginal feed 'stock and the extent of purification required. Ordinarilyit is preferred to carry out this operation at temperatures of from 200to 600F.

Hydrocarbon iiow rates through the polymerization reactor under theconditions of this disclosure range from 0.5 to liquid volumes pervolume of catalyst per hour although the preferred rates are ordinarilythose of 1 to 4 volumes per hour.

A third stage catalytic alkylation treatment of the benzene-containingproduct stream is another novel feature of the present process. The feedto the alkylation reactor is comprised of the 160-180 F. fraction whichhas previously been treated for sulfur and olefin removal and a lightparain-olefm cut derived from the gaseous products produced in thearomatization operation. A silica-alumina catalyst is employed attemperatures of from about 200 to 700 F. with the preferred temperaturebeing about 450 F. Operating pressures are chosen in accordance withreaction requirements and may vary from about 100 to 1000 pounds. Thearomatics-olen feed is adjusted 'so that the benzene to olefin mol ratiolies between about l and 4. v

In order to further illustrate the specific uses and advantages of thepresent invention, the following exemplary operation will be described.However, since numerous other process modifications will be obvious inthe light of the foregoing disclosure, no undue limitations areintended.

Eample The operation as described herein was carried out substantiallyas indicated in the drawing to prepare an aviation base stock boilingbetween 200-350 F. and containing the products derived from thealkylation of the benzene stream with a Cz-C4 olefin-parain cut.

The charge to the rst stage catalytic aromatization reaction was apolyform gasoline of 405 F. end-point and 50.1 A. P. I. gravity. i Theaverage temperature of the bauxite catalyst bed was maintained between1100-l200 F. under a pressure of 85 p. s. i. and at a feed ow-rate ofabout 6 barrels per ton of catalyst per hour. After stabilization, theyield of butane-free gasoline` amounted to 65 weight per cent based onthe charge. This stabilized material was clay-treated and furtherfractionated into cuts having boiling ranges of 80-200 F. and 200-350F., respectively.

The lower boiling fraction represented 18.6 weight per cent of thecharge and was found to contain 21.5 per cent benzene, about 12 per centolefin and 0.270 weight per cent sulfur. In order 160-180 F. fractionComposition, Wt. percent Untreated Treated Benzene 60 68 Olen 17 6Paraln 13 l5 Naphthene 10 l1 Sulfur 0. 275 0.127

The treated benzene concentrate was subjected to alkylation with atypical C2-C4 fraction of light gas produced in the aromatizationoperation. The gas contained approximately equimolecular proportions ofethylene, propylene and butylenes admixed with the correspondingparaffins such that about volume per cent of the gas was olefinic. Thealkylation was carried out at a pressure of 1000 p. s. i. at atemperature of about 500 F. and with a feed rate of 2 volumes per hourper volume of catalyst. The mol ratio of benzene to olen was maintainedat 1:1 in order to obtain maximum conversion of benzene. The effluenthydrocarbon was stabilized and fractionated to yield the following data:

Wt. per cent benzene reacted '71 Wt. per cent alkylate overhead at 350 F73 The weight of 350 F. end-point alkylate realized is approximately thesame as the weight of benzene charged. However, the rich-mixtureblending value of the alkylate is about twice that of f the benzene,hence the alkylation procedure has resulted in a blending stock equal toabout twice the weight of benzene originally produced. In addition, 29weight per cent of the benzene is now available for recycle as such,while the kettle product will contribute valuable aromatics on furthercracking treatment as recycle stock.

The crude aviation blending stock of 200-350 F. boiling range wastreated over the silica-alumina catalyst under conditions identical withthose employed in treating the light fraction and the eiiluent was rerunto give a finished 200-350 F. blending stock. The improvement in qualityas a result of the polymerizing treatment is shown in the followingtabulation:

2004350o F. Stock Untreated Treated Sulfur, wt. per cent 0. 279 0. 160Broniine number 10 4. 0 37. 1 36. 8

The yield of the nished blending stock was 46.4 weight per cent based onthe original charge to the aromatization step. Since the originalbenzene yield was 4.0 per centon the same basis and since the amount ofalkylate produced was approximately equal to the original benzene, the

9 overall yield of G-350 F. stock on addition of the alkylate amountedto 50.4 per cent.

The addition of the high-quality alkylate which amounts to about 8 percent of the nal 20D-350 F. stock increased the rich rating from 2.91 to4.0 m1. of TEL in S-reference fuel, thus eiective- 1y transforming amoderately good blending stock into a high quality product.

We claim:

1. In a hydrocarbon conversion process of the class described, the stepscomprising subjecting a stream of a hydrocarbon feed stock comprising apetroleum distillate having a relatively high carbon to hydrogen ratioto cracking under cyclization conditions in the presence of anaromatizing catalyst at a temperature of between 1050-1250o F.;separating eiiluent from the preceding step into a first fractioncomprising normally gaseous olenic material, a, normally liquid about200 F. end-point second fraction, and a third fraction boiling betweenabout 20G-350 F.; polymerizing a stream of the second fraction thepresence of a polymerization catalyst to effect substantial reduction inolen and sulfur content; recovering a benzene-concentrate from effluentfrom the polymerization step; alkylating a stream oi thebenzene-concentrate with at least Dart of said first fraction; recyclingat least part of the unreacted eiiluent from the alkylation step to thestream of feed stock; and transmitting reacted efuent from thealkylation step to effluent from the cracking step.

2. The process in accordance with claim l wherein a stream of the thirdfraction is treated under polymerizing conditions and the so treatedthird fraction is then fractionated to recover a fraction boilingbetween about 20G-350 F. and substantially free of sulfur compounds.

3. The process in accordance with claim l. wherein the indiivdualcracking and polymerizing steps are each carried out in the presence ofa corresponding suitable catalyst material.

4. The process in accordance with claim l wherein the cracking step iscarried out in the presence of a bauxite catalyst and the polymerizingsteps are each carried out in the presence of a silica-alumina catalyst.

5. In a process for the manufacture of aviation gasoline blending stockhaving a high concentration of aromatic hydrocarbons, the stepscomprising aromatizing a stream of a feed stock comprising hydrocarbonsof relatively high carbon to hydrogen ratio and boiling between about150- 400 F. in the presence of an aromatizing catalyst at a temperaturebetween 1050-l250 F.; recovering from efliuent from the preceding step afirst fraction comprising normally gaseous olennic material, a normallyliquid about 200 F. enolpoint second fraction. and a third fractionboiling between about 200-350o F.; polymerizing a stream of the secondfraction in the presence of a catalyst to effect substantial reductionof olefin and sulfur content; fractionating a stream of eliluent fromthe last named step to obtain a benzene fraction boiling between about160-180 F.; alkylating said benzene fraction with said first fraction inthe presence of a catalyst; recycling unreacted effluent from thealkylation step to the stream of feed stock; transmitting total alkylatefrom the eiiluent from the alkylation step to eli'luent from thearomatization step at such a point that said total alkylate may befurther treated along with reacted products of said aromatizing step;and polymerizing the final third fraction in the presence of a 10catalyst to elect removal of olefin and sulfur content.

6. 1n a. process for the manufacture of aviation gasoline blending stockhaving a high concentration of aromatic hydrocarbons, the stepscomprising aroinatizing a stream of a feed stock comprising hydrocarbonsof relatively high carbon to hydrogen ratio and boiling between about150- 400 F. in the presence of a catalyst; separating eiiuent from thepreceding step to obtain a normally gaseous fraction comprising Cl andlighter cleins and a normally liquid fraction comprising about 350 F.end-point reacted eliluent, fractionating said liquid fraction to obtaina 200 F. endpoint fraction and a fraction boiling between 20G-350 F.;polymerizing a stream of the 200 F. end-point fraction in the presenceof a catalyst to effect substantial reduction of olefin and sulfurcontent; fracticnating stream of eiluent from the last named step toobtain a benzene fraction boiling between about i60-180 F.; alkylatingsaid benzene fraction with said normali gaseous fraction in the presenceof a catalyst; recycling unreacted eiiiuent from the alkylation step tothe stream of feed stock; recycling total alkylate from the eiiluent 0fthe alkylation step to the 350 F. end-point liquid fraction;polymerizing the final 20G-350 F. boiling fraction in the presence of acatalyst; and separating a substantially olen and sulfur free productboiling between 20o-350 F. from eiiuent from the last mentioned step.

'7. The process in accordance with claim 6 wherein the aromatizing stepis carried out in the presence of an aiumina base catalyst and thealkylatinT and polymerizing steps are each carried out in the presenceof a corresponding silicaalumina catalyst.

8. The process in accordance with claim 6 wherein the aromatizing stepis carried out at temperatures within the range of 1050-l250 F. and atpressures within the range of atmospheric to 200 pounds per square inchgauge; wherein the polyrnerizing steps are each carried out attemperatures within the range of 200-600 F. and at pressures within therange of G-1500 pounds per square inch gauge; and wherein the alkylatingstepl is carried out at temperatures within the range of 20G-700 F, andat pressures within the range of 1004.000 pounds per square inch gauge.

9. The process in accordance with claim 6 wherein the aromatizing stepis carried out at temperatures within the range of 1050-1250 F. and atpressures within the range of atmospheric to 200 pounds per square inchgauge in the presence of an alumina base catalyst; wherein thepolymerizing steps are each carried out at temperatures within the rangeof 20D-600 F. and at pressures within the range of 80G-1500 pounds persquare inch gauge in the presence of a corresponding silica-aluminacatalyst; and wherein the alkylating step is carried out at temperatureswithin the range of 20G-'700 F. and at pressures within the range of10G-1000 pounds per square inch gauge in the presence of asilica-alumina catalyst.

10. The process as in claim 6 characterized by the alkylation of thebenzene fraction with ethylene segregated from the normally gaseousfraction.

l1. The process as in claim 6 characterized by the alkylation of thebenzene fraction with propylene segregated from the normally gaseousfraction.

12. The process as in claim 6 characterized by the alkylation of thebenzene fraction with butyl- 1l 12 ene segregated from the normallygaseous frac- 350 F. and a higher-boiling fraction containing tion.polymers and sulfur compounds, and said higher- 13. The process inaccordance with claim 6 boiling fraction is recycled to the feed stockwherein effluent from the second polymerzng stream,

step is separated into a substantially olefin and WALTER A. SCHULZE.sulfur free product fraction boiling between 2.00- 5 CARL J. HELMERS.

